To form thin films of a uniform film thickness on a base material at a low cost in a production process for semiconductors, optical disks, etc.

A coating soln. is dropped from a discharge nozzle 4 onto the surface of the base material 2 to be coated which is placed on a horizontal turn table in this device. The thin film is formed by rotating the base material. After the coating soln. is dropped from the nozzle 4, the nozzle front end 4a under standing by is immersed and held into the soln. 10 for nozzle immersion of a compsn. approximate to or equal to the compsn. of the coating soln. The crystal deposition of the solute is suppressed. The method is particularly useful in the case of applying the soln. contg. the solute having high crystallinity.